Electronic systems may be composed of a plurality of sub-modules or components that may be connected to each other via wires, cables, conductive traces (in the case of printed circuit boards or semiconductor chips), etc.
Some components only have a small number of connections that can be used for a transmission of information to and/or from the component. On some occasions it may be desired to facilitate an access to the component for a diagnosis module in an easy manner, i.e. the access from the diagnosis module to the component requiring the establishment of a few connections only, but nevertheless enabling a transmission of information to the component as well as receiving (or reading out) information from the component.
Such an ability to communicate with the component may be desirable in order to, e.g. activate test modes of an integrated circuit, inspect or debug component internals, to (initially) configure and/or calibrate the component—for example by means of e-fuses, an electrically erasable programmable read only memory (EEPROM) or other one-time-programmable (OTP) or programmable functions—or to enable clients (buyers or users of the component) to perform a parameterization of the component by themselves.
In view of these situations requiring a communication with the component it may be desirable to keep the number of connections small in order to design the integration of the component as easily as possible for a client-specific application, or to facilitate a use of the component with products having a low number of pins or products that cannot afford to use many pins dedicated to this purpose. This can be required due to (but not limited to) economic reasons (e.g. cost of copper) or construction reasons (either mechanical: e.g. limited room for connectivity or electrical: e.g. to achieve a better energy efficiency or re-use existing, but for a specific application not needed or due to a given setup mandatory, connections).